In vacuum transistors, the traditional semiconductor channel material commonly found in field effect transistors is replaced with a vacuum channel. See, for example, Han et al., “Vacuum nanoelectronics” Back to the future?—Gate insulated nanoscale vacuum channel transistor,” Applied Physics Letters 100, pgs. 213505-1-213505-4 (May 2012).
Vacuum transistors are useful for the next generation high speed and low-power electronics. For instance, vacuum transistors offer high speed performance with the potential to reach terahertz (THz) operation with zero body-to-gate-capacitance and ballistic transport of electrons. They operate at low power with the potential to achieve sub-threshold swing less than 60 millivolts per decade (mV/dec) with scaled dielectrics.
However, conventional vacuum transistors have several notable drawbacks. High voltage is needed to induce field emission. For instance, 1-10 volts are needed for current silicon-based devices. These devices also have a low field emission current density. See, for example, Srisonphan et al., “Metal-oxide-semiconductor field-effect transistor with a vacuum channel,” Nature Nanotechnology 7, 504-508 (July 2012).
Therefore, improved vacuum transistor designs which do not suffer from the above-described drawbacks would be desirable.